The present invention provides a method for preparing an ultra-thin material on insulator through adsorption by a doped ultra-thin layer. In the method, first, an ultra-thin doped single crystal film and an ultra-thin top film (or contains a buffer layer) are successively and epitaxially grown on a first substrate, and then a high-quality ultra-thin material on insulator is prepared through ion implantation and a bonding process. A thickness of the prepared ultra-thin material on insulator ranges from 5 nm to 50 nm. In the present invention, the ultra-thin doped single crystal film adsorbs the implanted ion, and a micro crack is then formed, so as to implement ion-cut; therefore, the roughness of a surface of a ion-cut material on insulator is small. In addition, an impurity atom strengthens an ion adsorption capability of the ultra-thin single crystal film, so that an ion implantation dose and the annealing temperature can be lowered in the preparation procedure, thereby effectively reducing the damage caused by the implantation to the top film, and achieving objectives of improving production efficiency and reducing the production cost.